Background preventer apparatus are well known in the art and in the past have been used in water distribution systems to prevent contamination of tne potable water portion by preventing backflow of fluid from the non-potable portion beyond a certain point in the system. Two conditions tend to cause backflow in a water distribution system. The first condition wnich could cause backflow is known as "backflow siphonage" and this occurs in the potable supply pipe or main when its pressure drops to cause a vacuum or partial vacuum of the system. This will cause a backflow of liquid from the service pipe and if the liquid in the service pipe is contaminated, will also contaminate the potable water supply. The second condition to cause backflow is a condition occurring in the service pipe or non-potable portion of the system. This condition results in a pressure condition when the pressure in the non-potable service pipe exceeds that in the potable supply pipe.
Heretofore backflow preventer devices have been primarily used in water distribution systems for large manufacturing plants and the like. The prior backflow preventer apparatus are quite large and expensive to manufacture and such devices were utilized by themselves rather than in combination with a water meter.
More recently efforts have been made to incorporate backflow preventer devices in a unit especially designed to include a water meter. Such prior efforts were rather costly to manufacture since the meter box had to be specifically designed to accommodate the size of the backflow preventer devices within the same. Other efforts were made to incorporate backflow preventer devices into a meter box installation but these systems lacked the capability of servicing the backflow preventer devices without disconnecting the installation from the service pipe and this oftentimes required digging around the meter box to make the disconnections.